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Discussion Starter · #1 ·
I've searched the forum and still can't find why my car is having random/multiple misfiring, the only code I'm getting is p0300 and p0171 which I figure is just because I'm running an aftermarket header, but p0171 was just recent. spark plugs, wires and coils are all fine, no vaccum leaks, compression is great, timing isn't off, and Injectors check out, and I've cleaned the MAF and throttle body.

The car will have a very ruff idle on cold start, kinda like it's bogging really bad but it never dies, I just let it bog and it smooths out and won't do it again until I start it when it's cold, when I start it when it's warm you can't even tell there's a misfire code, but all I'm getting told is that it's just the p0300 it won't tell me that there's certain cylinders missing.
 

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P0300 is multiple cylinder misfire. This code pops up when it isn't just a certain cylinder or two that's missing.

How have you verified that plugs, coils and wires are fine? Those, along with vacuum leaks and coil connectors are the #1 cause of misfire.
 

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Discussion Starter · #3 ·
P0300 is multiple cylinder misfire. This code pops up when it isn't just a certain cylinder or two that's missing.

How have you verified that plugs, coils and wires are fine? Those, along with vacuum leaks and coil connectors are the #1 cause of misfire.
Yeah I have verified all of those checked out, the CEL will never stay on, after a few days of it being on it won't show for about a day or two then it'll pop back up, but once the idle smooths out it never gives me an issue driving wise until I go to cold start it again.
 

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Discussion Starter · #5 ·
Bet you have a vacuum leak. You just haven’t found it yet.
So after a long a long month and a half about just trouble shooting I still have this p0300, I tested the cars vaccum system about 4 times, replaced 2 hoses and even redone the coil pack connectors for the car, and still nothing, the injectors have a proper spray pattern and aren't clogged, and I've cleaned the MAF, any other ideas?
 

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So after a long a long month and a half about just trouble shooting I still have this p0300, I tested the cars vaccum system about 4 times, replaced 2 hoses and even redone the coil pack connectors for the car, and still nothing, the injectors have a proper spray pattern and aren't clogged, and I've cleaned the MAF, any other ideas?
Did the 171 cel go away?
 

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Okay, I assume you have checked the connectors on the coils, ignitor, cam position, VVTi solenoid, and crank sensor. Did you inspect the crank timing reluctor?
 

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Discussion Starter · #10 ·
Okay, I assume you have checked the connectors on the coils, ignitor, cam position, VVTi solenoid, and crank sensor. Did you inspect the crank timing reluctor?
Crank sensor checked out perfectly, car has now been starting to hesitate and sputter under hard acceleration as well, it'll pop and crackle when it's stuttering then finally start to move after a solid 3 seconds of just popping, it's kinda like anti lag lol
 

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UPDATE**
I pulled out the code reader and not it's giving me 3 extra codes, p0301,p0302, and p0303, so now it's telling me specific cylinders
Look at those coils and connectors. Try swaping coils with cylinders and see if the codes move to those cylinders. If not look at the reluctor on the crank. The app sensor is the one on the throttle body where the cable attaches. Accelerator pedal position =APP
 
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